Compression over-molding container preforms

ABSTRACT

A method of making a preform for blow molding a plastic container. In one embodiment, a tubular shell of plastic construction is provided, wherein the shell has a closed end and an open end. A plastic mold charge is then placed within the shell, and a preform body is compression molded within the shell such that the shell is secured to an outer surface of the preform body. In another embodiment, a tubular shell of plastic construction is provided wherein the shell is open at opposed ends, and a preform body is then compression molded externally around the shell. A preform for blow molding a plastic container includes a plastic shell and a plastic body that is compression over-molded to the plastic shell.

The present invention is directed to compression molding preforms forsubsequent blow molding as plastic containers, and more particularly toan article and a method for compression over-molding a preform within oraround a pre-made shell.

BACKGROUND AND SUMMARY OF THE INVENTION

In the production of hollow plastic containers it is common to form aparison or preform, and then to blow mold the preform to achieve thefinal shape of a container. The preform typically is injection molded,and includes a body having a closed bottom end and a sidewall extendingin a direction axially away from the closed bottom end. The preform alsoincludes a neck, which axially terminates the sidewall to define an openend of the preform. The perform neck can have one or more threads forreceiving a threaded closure to close the container.

A method in accordance with one aspect of the invention includes makinga preform for blow molding a plastic container. According to the method,a tubular shell of plastic construction has a closed end and an openend. A plastic mold charge is placed within the shell, and a preformbody is compression molded within the shell such that the shell issecured to an outer surface of the preform body.

In accordance with a second aspect of the invention, there is providedanother method of making a preform for blow molding a plastic container.According to this method, a tubular shell of plastic construction isprovided wherein the shell is open at opposed ends, and a preform bodyis compression molded externally around the shell.

An article in accordance with a third aspect of the invention includes apreform that is used in the blow molding of a plastic container. Thepreform includes a plastic shell and a plastic body that is compressionover-molded to the plastic shell.

BRIEF DESCRIPTION OF THE DRAWING

The invention, together with additional objects, features, advantagesand aspects thereof, will be best understood from the followingdescription, the appended claims and the accompanying drawings, inwhich:

FIG. 1A illustrates a compression molding apparatus according to oneexemplary embodiment of the present invention in which a charge ofpreform material is located within a pre-made shell, which is insertedwithin a mold cavity;

FIG. 1B illustrates the compression molding apparatus of FIG. 1A whereina core pin has been driven into the mold cavity to compression over-moldthe preform material within the pre-made shell to produce a completedpreform;

FIG. 2 illustrates the completed preform produced by the apparatus ofFIG. 1B;

FIG. 2A illustrates an enlarged view of a sidewall of the preform ofFIG. 2;

FIG. 2B illustrates an enlarged view of a sidewall according to analternative embodiment of the present invention in which the preformmaterial is multilayered;

FIG. 2C illustrates an enlarged view of a sidewall according to analternative embodiment of the present invention in which the shellmaterial is multilayered;

FIG. 3 illustrates a compression molding apparatus according to anotherexemplary embodiment of the present invention in which a charge ofpreform material is located within a compression mold cavity and apre-made shell is loaded to a compression core pin;

FIG. 4 illustrates a preform produced by the apparatus of FIG. 3, inwhich the preform material is compression over-molded around thepre-made shell;

FIG. 5 illustrates a preform according to an alternative embodiment ofthe present invention wherein the pre-made shell is substantiallytubular without a flange at an upper end thereof; and

FIG. 6 illustrates a preform according to an alternative embodiment ofthe present invention wherein the preform material has been compressionmolded within the pre-made shell.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In general, the present invention relates to a method of making amulti-layer parison or preform by compression molding, and to theresulting preform, wherein the preform is adapted subsequently to bemolded into a plastic container. Referring now to the drawing figures,FIGS. 1A through 2C illustrate a first exemplary embodiment of thepresent invention. FIG. 1A illustrates a compression molding apparatus10 that is used in accordance with a process of the present invention.The compression molding apparatus 10 includes a core pin 12 positionedabove a compression mold 14. The compression mold 14 includes a closedbottom end 16, a body portion 18, and a finish portion 20 that define amold cavity 22.

A pre-made component, liner, sleeve or shell 24 is placed in thecompression molding apparatus 10 prior to compression molding. In theembodiment of FIG. 1A, the pre-made shell 24 preferably is composed of arelatively inexpensive polymeric material such as a regrind polymer,post consumer resin, lower IV material and the like. The shell 24 iscircumferentially continuous and may be produced in an upstreammanufacturing operation such as injection molding, thermoforming,cutting from swaged tube stock or the like. In any case, this embodimentinvolves loading the shell 24 all the way down into the mold cavity 22of the mold 14, such that the top of the shell 24 is positioned justbelow the finish portion 20 of the mold 14.

A compression overmolding process follows, wherein a charge 26 ofpolymeric material is placed or fed into the mold cavity 22 within theinterior of the shell 24. The charge 26 is soft or molten, and therebyconforms to and fills the lower end of the shell 24. The core pin 12 andmold 14 are positioned in vertical alignment, and the core pin 12 ismoved into the mold 14 to compression mold the charge 26 over and withinthe interior of the shell 24. As shown in FIG. 1B, a preform body 28 isthus molded over the shell 24 between the core pin 12 and mold 14. Moldcharge 26 can be of any suitable polymer intent, such as polyester,including polyethylene terephthalate (PET) and polyethylene naphthalate(PEN).

FIG. 2 illustrates a preform 30 produced by the apparatus and processdescribed above. The preform 30 includes a closed bottom end 32 definedby a closed bottom end 32 a of the shell 24 and by a closed bottom end32 b of the preform body 28. A sidewall 34 extends in a directionaxially away from the closed bottom end 32, and terminates in an openend 36 opposite from the closed bottom end 32. The preform body 28 isformed within the shell 24, such that the shell 24 is secured to theouter surface of the preform body 28. The preform body 28 extends fromthe closed bottom end 32 to the open end 36 where the preform body 28includes a finish portion 38 and a flange 40. In contrast, the shell 24does not extend all the way from the closed bottom end 32 to the openend 36 but, rather, stops short at an open end 42 just beneath theflange 40 of the preform body 28.

FIGS. 2A-2C generally illustrate enlarged views of the sidewall 34 ofthe preform 30 of FIG. 2. FIG. 2A illustrates an enlarged portion of thesidewall 34 showing the shell 24 disposed on the outside of the preformbody 28, wherein both the shell 24 and preform body 28 are of monolayerconstruction. FIG. 2B illustrates a sidewall 134 according to analternative embodiment of the present invention wherein the shell 24 isof monolayer construction, but an alternative preform body 128 iscomposed of multiple layers, such as three layers as shown. Similarly,FIG. 2C illustrates another sidewall 234 according to anotheralternative embodiment of the present invention wherein the preform body28 is a of monolayer construction, but an alternative shell 224 iscomposed of multiple layers, such as three layers as shown. In FIGS. 2Band 2C, the multiple-layers may be composed of, for example, outsidelayers of virgin PET and an interior layer of barrier resin such asnylon or ethylene vinyl alcohol (EVOH). In another example, the outsidelayers may be composed of different materials such as virgin PET andpost consumer resin. A method for compression molding such stratifiedlayers is disclosed in U.S. application Ser. No. 10/746,404, which isassigned to the assignee hereof and is incorporated by reference herein.

Regardless of whether the preform body 28 or 128 or the shell 24 or 124,is individually composed of single or multiple layers, the preform 30preferably is composed in a ratio of about 90% regrind polymer, postconsumer resin, lower IV material, or the like and about 10% virginpolymer, which preferably is composed of about 10% polycarbonate,polycarbonate blends, PEN or PEN blends and about 90% PET for low cost,high temperature applications. More specifically, it is preferred thatthe shell be composed of about 10% high IV or high temperature polymericmaterial and about 90% low IV polymeric material. (IV is intrinsicviscosity measured according to ASTM D-5225-92.)

Referring now to FIGS. 3 through 5, there is illustrated a secondexemplary embodiment of the present invention. FIG. 3 illustrates acompression molding apparatus 310 that is used in accordance with ofthis second embodiment of the present invention. The compression moldingapparatus 310 includes a core pin 312 positioned above a compressionmold 314. The compression mold 314 includes a closed bottom end 316, asubstantially cylindrical body portion 318 and a finish portion 320 thattogether define a mold cavity 322. As with the embodiment of FIGS. 1Athrough 2C, this embodiment involves novel steps to produce amulti-layer preform.

A pre-made component, liner, sleeve, tube or shell 324 is loaded intothe compression molding apparatus 310 prior to compression molding. Inthis embodiment, the pre-made shell 324 preferably is composed of anypolymeric material, such as virgin PET or the like, that is amenable foruse with containers—e.g., for holding contents for human consumption.The shell 324 may be produced by a process involving injection molding,thermoforming, cutting from swaged tube-stock or the like. In any case,this embodiment involves loading the shell 324 onto and around the corepin 312. The shell 324 includes a flange portion 323 that abuts aflanged portion of the core pin 312, and further includes an open bottomend 325. It is, however, contemplated that the bottom end 325 insteadmay be closed.

A compression overmolding process follows, wherein a charge 326 ofpolymeric material is placed or otherwise fed into the mold cavity 322.The charge 326 is soft or molten, and thereby conforms to and fills thelower end of the mold cavity 322. The core pin 312, with the shell 324mounted thereto, and the mold 314 are positioned in vertical alignment,and the core pin 312 and shell 324 are moved into the mold 314 tocompression mold the charge 326 over and around the exterior of theshell 324.

FIG. 4 illustrates a completed preform 330 produced by the apparatus andprocess described immediately above. The preform 330 includes a closedbottom end 332, a sidewall 334 extending in a direction axially awayfrom the closed bottom end 332, and an open end 336 opposite of theclosed bottom end 332. The compression molding of the charge 326 of FIG.3 results in the formation of a preform body 328 over and around theexterior of the shell 324. The preform body 328 extends from the closedbottom end 332 to the open end 336, where the preform body 328 includesa finish portion 338 and a flange 340. In contrast, the shell 324extends from its flange 323 at the open end 336 toward the closed bottomend 332, but stops just short at about a transition point between thesidewall 334 and the closed bottom end 332. In a modification of thisembodiment, FIG. 5 illustrates a preform 430 having a shell 424 made bythe process of the present invention, but not including the flange 323of the shell 324 of FIG. 4. Rather, the shell 424 is a tubular-shapedcomponent having an open upper end 423 opposite an open lower end 425.

As with the embodiment of FIGS. 1A through 2C, in this embodiment thepreform body 328 and shell 324, or 424 may be composed of multi-layermaterials. Moreover, the shell 324, or 424 preferably is composed ofvirgin polymer, and the preform body 328 composed of a regrind material,post consumer resin, low IV material or the like. Where the preform body328 may be composed of multiple layers, it is preferable that theinnermost layer, which partially defines the interior of the preform 330or 430, be composed of a virgin polymer, and the other layers may becomposed of regrind material or the like.

FIG. 6 illustrates a modification to the embodiment depicted in FIG. 2.Here, a preform 530 includes a preform body 528 that is partiallycircumscribed by a modified shell 524. The shell 524 of this embodimentincludes a flange 523 that abuts a flange 540 of the preform body 528,and the shell 524 does not extend all the way from the flange 540 downand around a closed bottom end 532 of the preform. Rather, the shell 524stops at about a transition point between the sidewall 534 of thepreform 530 and the closed bottom end 532.

With all of the embodiments and modifications described above, thepresent invention provides a process for making a preform that iscomposed of layers of materials so as to reduce material costs yetoptimize container properties such as strength and resistance to gaspermeability.

There have thus been described a method and apparatus for compressionovermolding a charge of polymeric material with respect to a pre-madesleeve, and a preform made by such method, that fully satisfy all of theobjects and aims previously set forth. The present invention has beendisclosed in conjunction with two exemplary presently preferredembodiments thereof, and a number of modifications and variations havebeen discussed. Other modifications and variations will readily suggestthemselves to persons of ordinary skill in the art in view of theforegoing description. Directional words such as “lower”, “bottom”, andthe like are employed by way of description and not limitation withrespect to the upright orientations of the components illustrated in thedrawings. The invention is intended to embrace all modifications andvariations as fall within the spirit and broad scope of the appendedclaims.

1. A method of making a preform for blow molding a plastic container, which includes the steps of: (a) providing a tubular shell of plastic construction, said shell having a closed end and an open end, (b) placing a plastic mold charge within said shell, and (c) compression molding a preform body within said shell such that said shell is secured to an outer surface of said preform body.
 2. The method set forth in claim 1 wherein said step (b) includes placing said mold charge within said closed end of said shell.
 3. The method set forth in claim 1 wherein said tubular shell is of multilayer plastic construction.
 4. The method of claim 3 wherein said tubular shell is composed of about 10% high IV material and about 90% low IV material.
 5. The method of claim 1 wherein said tubular shell is of single layer plastic construction.
 6. The method of claim 5 wherein said tubular shell is composed of at least one of a regrind polymer, post consumer resin and a low IV material.
 7. The method of claim 1 wherein said preform is composed of about 90% low cost material such as a regrind polymer, post consumer resin, lower IV material and the like, and is further composed of about 10% virgin material.
 8. The method of claim 7 wherein said 10% virgin material is composed of about 10% polycarbonate, polycarbonate blends, PEN or PEN blends, and about 90% PET.
 9. The method of claim 1 wherein said step (c) includes molding a preform finish integrally with said body and adjacent to but outside of said open end of said shell.
 10. A preform for blow molding a plastic container wherein said preform is produced by the method of claim
 1. 11. A method of making a preform for blow molding a plastic container, which includes: (a) providing a tubular shell of plastic construction, said shell being open at opposed ends, and (b) compression molding a preform body externally around said shell.
 12. The method of claim 11 wherein said tubular shell is composed of a virgin polymer composed of about 10% polycarbonate, polycarbonate blends, PEN or PEN blends, and about 90% PET.
 13. The method of claim 11 wherein said tubular shell includes a flange portion at one of said opposed ends.
 14. The method of claim II wherein said tubular shell is composed of a multi-layer material including at least one layer of virgin polymer and at least one layer of a low cost material such as a regrind polymer, post consumer resin, lower IV material, and the like.
 15. The method of claim 11 wherein said preform body is composed of a multi-layer material including at least one layer of virgin polymer and at least one layer of a low cost material such as a regrind polymer, post consumer resin, lower IV material, and the like.
 16. The method of claim 11 wherein said preform is composed of about 90% low cost material such as a regrind polymer, post consumer resin, lower IV material, and the like and is further composed of about 10% virgin material.
 17. The method of claim 11 further comprising loading said tubular shell to a core pin prior to said compression molding step.
 18. The method of claim 11 wherein said step (b) includes molding a preform finish integrally with said preform body and adjacent to but outside of said open end of said shell.
 19. A preform for blow molding a plastic container wherein said preform is produced by the method of claim
 11. 20. A method of making a preform for blow molding a plastic container, said method includes: providing a shell, loading said shell to one of a compression mold cavity and a compression core pin, introducing a softened polymer into said compression mold cavity, and compression molding said softened polymer to said shell.
 21. The method of claim 20 wherein said loading step includes loading said shell to said compression mold cavity and said introducing step includes introducing said softened polymer at least partially within said shell and said compression molding step includes compression molding said softened polymer at least partially within said shell.
 22. The method of claim 21 wherein said shell is a substantially open-ended tubular-shaped component.
 23. The method of claim 20 wherein said loading step includes loading said shell to said compression core pin and said compression molding step includes compression molding said softened polymer at least partially around said shell.
 24. The method of claim 20 wherein said shell is a tubular-shaped component having a flange portion at one end thereof.
 25. A preform for blow molding a plastic container wherein said preform is produced by the method of claim
 20. 26. A preform for blow molding a plastic container, said preform including: a plastic shell; and a plastic body compression over-molded to said plastic shell.
 27. The preform of claim 26 wherein said plastic body is compression over-molded at least partially around said plastic shell.
 28. The preform of claim 26 wherein said plastic body is compression over-molded at least partially within said plastic shell. 